The 3 side rumford draws great. Keep in mind though I have a 8" fresh air vent in the bottom of the firebox. I am also closing the front of the firebox with fire rated glass to protect a piano that is 5 feet from the front of the fireplace. We considered closing the sides instead of the front but really donšt want to over heat the piano so we are doing the front instead. I am so pleased with your plans and detailed designs.

Thanks,
Allan